Why It's So Hard to Figure Out the Real Dangers of Stoned Driving

Photo by Anthony Camera
Recent Colorado Department of Transportation figures show that stoned-driving fatalities went down from 2016 to 2017 for those over the legal intoxication limit but up in fatal crashes involving drivers who tested positive for any marijuana in their system, whether above the line or under it. Such mixed results are typical according to a new report, which acknowledges that getting firm answers about the risks involved with driving high remains an enormous challenge.

And there are plenty of reasons why.

The study in question, "Driving Under the Influence of Drugs and Alcohol," was issued by the Colorado Division of Criminal Justice and is accessible below in its entirety. Created in conjunction with House Bill 17-1315, which ordered the division "to report annually to the general assembly certain data relating to substance-affected driving citations that occurred in the previous year," it's filled with fascinating information, as indicated by our recent post headlined "In 15 Colorado Counties, DUI Totals Are More Than 1 Percent of the Population."

Among the most intriguing passages are frank admissions about the difficulties of reaching definitive conclusions in regard to stoned driving. Continue for examples grouped in four main categories and illustrated by graphics from the report.

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Colorado Division of Criminal Justice
Challenges in Marijuana Research

Despite many legislative and political attempts, cannabis remains a federal Schedule I drug — meaning that it has no officially recognized medical value. As such, the report notes, researchers wishing to study marijuana must register with the Drug Enforcement Administration "by submitting protocols detailing the substances involved, including the amount of each substance, and providing detailed security arrangements intended to prevent diversion of the drug to outside parties."

That's only the beginning of the complications.

Since 1968, the National Institute of Drug Abuse has contracted with the University of Mississippi, which grows the only marijuana available for federally sanctioned research use. However, the report reveals that "this Mississippi marijuana is of lower Delta-9 THC potency than what is being sold in the legal market, with 'High THC' defined as 5-10 percent and 'Very High THC' as above 10 percent."

In truth, most of the marijuana currently being sold in Colorado's recreational market tends to hover around 20 percent potency. "This discrepancy makes it difficult to generalize the study findings from impaired driving experimental protocols to real-world situations," the study's authors concede.

Local approval for research is no snap, either. The study depicts the registration process at the University of Colorado Denver's Anschutz Medical Campus as "lengthy (4-8 weeks) and elaborate, with a visit or phone interview to review security measures" — and once permission is granted, "there is extensive record-keeping required, and researchers are subject to annual audits by the Environmental Health and Safety Office of the University. Furthermore, there are potentially significant fiscal consequences for researchers and universities involved in marijuana research if there are deviations or mistakes in following the guidelines set forth."

More issues arise when it comes to the consistency of research, or a lack thereof. The study points out that some researchers focus on Delta-9 THC, "the psychoactive component of marijuana" that tends to indicate recent use when present at high levels. But "many people cite research or statistics that describe the presence of other cannabinoids," including ones that "can be detected many days later and are not necessarily indicative of recent use. A person can have cannabis metabolites present in their system while having none of the psychoactive effects of cannabis."

What's left unstated in this paragraph is that anti-marijuana advocates have long attempted to blur the distinctions between these types of cannabinoids as part of their efforts to demonize the substance. Plenty of studies have agendas, and figuring out what they are can require vigorous detective work.

In addition, the report argues that the "multiple methods of consumption" make marijuana a tough research topic. For instance, "cannabis can be smoked or vaped in its flower form, vaped or dabbed and inhaled in its concentrate form (wax, shatter, oil, resin), ingested in its edible form and even puffed through an inhaler. The onset of effects from edible cannabis can take 45 minutes to two hours, while the onset of smoked or vaped cannabis is within the first ten minutes."
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Colorado Division of Criminal Justice
Detection and Law Enforcement Training

The main ways of detecting marijuana impairment, the report states, "are behavioral and toxicological. The former comes in the form of observations by law enforcement officers during psychophysical roadside tests, and the latter comes in the form of chemical tests of breath and bodily fluids."

When in the behavior-assessment mode, officers in Colorado are likely to use one of three main approaches: Advanced Roadside Impaired Driving Enforcement (ARIDE), Drug Recognition Expert Training (DRE) or Standardized Field Sobriety Testing (SFST). Trainings in this last methodology are supplemented by so-called wet labs, at which "law enforcement can participate in mock contact with a volunteer who has or has not consumed alcohol. The consumption is concealed and occurs in a separate setting from officers. Law enforcement interacts with these volunteers as though they are suspected of impaired driving and implement the battery of tests to detect and assess impairment."

In contrast, there's only one marijuana-focused training lab in the entire state: "The Green Lab," set up in September 2015. As of July 2018, only 410 law enforcers in the state had undergone training at the facility, as compared to 5,674 active SFST operators.

The report maintains that "training to detect drugged driving impairment is critical for peace officers because there is no equivalent to the preliminary breath alcohol test (PBAT) for other drugs." But it's simply not happening at a level comparable to educational efforts pertaining to alcohol intoxication.

Field Sobriety Efficacy and Delta-THC Levels

Police officers frequently try to employ the same field tests used to determine alcohol impairment on drivers they think may be stoned. Some work okay, the authors of the report state; others, not so much.

Cited is a 2016 study that found the Horizontal Gaze Nystagmus analysis that's a staple of roadside testing for suspected drunk drivers "is not exhibited or expected in cannabis consumers." In contrast, the Lack of Convergence test was "a strong indicator of cannabis presence," as were the One Leg Stand and the Walk and Turn. Yet "despite individuals exhibiting clues of impairment during these standardized roadside tests, no correlation was found between the tests and Delta-9 THC concentration in whole-blood samples," the report acknowledges.

Another study found that pupil dilation, elevated pulse, the Lack of Convergence test and "the exhibition of impairment clues in two other psychophysical tasks were best at indicating impairment. However, the latter results were only for exams administered by Drug Recognition Experts. Again, there was no correlation in this study between test performance and whole-blood THC."

In recent years, manufacturers have attempted to come up with a cannabis equivalent for preliminary breath alcohol tests, which aren't admissible in court but are considered to be good screening tools. But a National Highway Traffic and Safety Admission study referenced in the report admits that the oral-fluid roadside tests developed to date "have not been shown to be completely reliable and accurate" when it comes to making distinctions between occasional and heavy users or the method of consumption.

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Colorado Division of Criminal Justice
Marijuana Impairment

A Colorado Department of Public Health and Environment review from last year found that "recent marijuana use increases a driver’s risk of a motor vehicle crash, less-than-weekly marijuana users exhibit meaningful driving impairment with THC levels of 2-5 ng/mL or ingestion of 10 mg or more of THC, combining marijuana and alcohol increases impairment and motor vehicle crash risk more than each alone" and "delaying driving for a minimum of six hours after smoking allows THC-induced impairment to resolve for less-than-weekly users at 18 mg of THC."

Still, the report stresses that plenty of uncertainties remain. One study cited by the authors determined that THC didn't have an effect on a driver's "time and distance perception," while another one found the opposite.  Likewise, a separate analysis showed that reaction time increased with THC impairment for both occasional and frequent users, while another one didn't register similar delays.

Such differences pop up again and again in the report. Take this excerpt: "Some studies find that, in comparison to drivers with no cannabis, there is no significant crash risk associated with cannabis impaired driving. However, other studies find that there is a higher crash risk associated with cannabis consumption."

So what's the truth? Researchers continue to seek it out — but as of now, consensus is hard to come by.

Click to read the Colorado Division of Criminal Justice's "Driving Under the Influence of Drugs and Alcohol" report.
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Michael Roberts has written for Westword since October 1990, serving stints as music editor and media columnist. He currently covers everything from breaking news and politics to sports and stories that defy categorization.
Contact: Michael Roberts